Every year, an estimated 400,000 seabirds worldwide are killed after getting unintentionally snared in gillnets while diving for food. A new review highlights that even penguins – the master swimmers of the avian world – aren’t safe from their clutches, and points the way to where the threat is most acute.

Long-time followers of BirdLife’s work will be very familiar with the ongoing issue of accidental seabird capture (or bycatch) in fisheries, which has driven declines in many globally threatened marine species. For over a decade, we have made remarkable progress in reducing albatross bycatch in collaboration with fishermen through our Albatross Task Force, both by designing and testing innovative solutions at-sea (such as bird-scaring lines), and through our advocacy work, which has helped to pass new national laws which have turned some of the world’s most deadly fisheries, such as those in Namibia, ‘seabird-safe’.

The death of albatrosses on longlines is a shocking reality; these majestic birds, capable of circumnavigating the globe, felled by a single fishing hook or trawl cable. But potentially more shocking is that penguins – the group of birds so well adapted to the ocean lifestyle that they have forgone flight altogether – are also drowned as a result of their encounters with fishing boats – this time, by getting entangled in fishing nets as they dive for food.

Until now, the exact impact of bycatch on penguins was poorly understood. But now, for the first time, a collaboration of penguin and fisheries experts the world over, led by BirdLife, has drawn together what is known of penguin bycatch to highlight the species most affected and the fishing gears with the greatest impact.

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The review, published in Endangered Species Research and the product of a collaboration initiated by Dr. Ursula Ellenberg at the 8th International Penguin Conference, found that of 18 species, 14 have been recorded as bycatch in fisheries. For many of these species, the records are sparse – and though the death of individual birds is unnecessary and undoubtedly sad, limited conservation resources dictate that our focus be drawn to those species for which bycatch levels are of greatest concern.

Gillnets are made from fine, near-invisible nylon that catches fish around the gills

To that end, the paper concludes that bycatch poses the greatest risk to three species – Humboldt Penguin Spheniscus humboldti (Vulnerable) and Magellanic Penguin Spheniscus magellanicus (Near Threatened), both found in South America, and the Yellow-eyed Penguin Megadyptes antipodes (Endangered), a remarkable-looking bird endemic to New Zealand. All of these species have been recorded as captures in gillnets – a fishing gear usually comprised of fine, near-invisible nylon that catches fish around the gills. The review reveals that Magellanic Penguins have also been caught in trawlers (vessels that pull large nets through the water behind them) off the coast of Argentina.

The impact of a number of individual fisheries on Magellanic Penguins has been assessed through the years, and individually, none of these has been deemed to be killing penguins in sufficient numbers to affect their populations. This includes industrial trawl vessels off the coast of Argentina and smaller-scale gillnetters in Argentina and southern Brazil. However, the cumulative impact of these fisheries – affecting penguins across their migratory route from the seas adjacent to the breeding grounds in Argentina and Chile to the non-breeding grounds off Brazil and Uruguay – has not been assessed. With the species listed as ‘Near Threatened’, the need to understand the impact of bycatch is pressing.

There are a lack of contemporary data on the bycatch of Humboldt Penguins, but historically high bycatch in Peruvian and Chilean gillnets again highlights a need to deploy observers on vessels overlapping with penguin distribution in key locations. The size of this fleet (over 10,000 vessels are thought to use gillnets in Peru alone) means this is no small undertaking, but the conservation status of Humboldt penguins – Vulnerable on the IUCN Red List – mean action is critical.

There is a very real risk that bycatch will give Yellow-eyed penguins a helping hand towards extinction

The bycatch of Yellow-eyed Penguins is of greater concern. Populations of these stunning but endangered birds are small and fragile, and while official estimates of bycatch in gillnets are relatively low, at 35 birds per year, this is likely to be an underestimate, owing to limited observer coverage in key Yellow-eyed Penguin feeding areas. Regardless, even this low estimate has the potential to contribute to the species’ demise, given its precarious status and low global population estimate of just 3,400. The recent crash of the important population on predator-free Codfish Island brings the issue into quick relief – without substantially increased observation of the New Zealand set-net fleet and management action, there is a very real risk that bycatch will give Yellow-eyed penguins a helping hand towards extinction.

BirdLife are working to develop technical solutions to the issue of gillnet bycatch. The implementation of such measures in trawl and longline fisheries has proven to be hugely effective in reducing albatross bycatch, partly because they allow fishermen to keep fishing while limiting their impact on non-target species. Identifying these measures for gillnets remains a challenge, but using the inspiration of our Albatross Task Force, we remain optimistic that one day we might follow a similar model to save penguins (and a whole host of other diving birds) from bycatch too.

One solution currently being tested is the development of black and white sheets, that are affixed to fishing nets and alert diving birds to their presence (gillnets are otherwise invisible to birds underwater). That said, it is clear from the global review that Humboldt, Magellanic and particularly Yellow-eyed penguins can’t afford to wait for technical fixes, especially in the face of myriad threats from climate change, invasive predators and habitat loss. In the short-term, efforts must be made improve observation of the fleets that pose a risk to penguins, so that targeted action can be taken to minimise the pointless and tragic loss of these charismatic birds.

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